A mercedes diesel engine is rebuildable by pretty much anybody just as long as you keep in mind that it is a fairly complex engine. Nothing to really worry about just remember that its not your standard sbc.

I've rebuilt a 300 engine. If you've got the time, the tools (nothing too exotic), and the inclination, do it. Why the heck not? You'll save a lot over having someone else do it for you. It's an engine made of high-quality parts, certainly, but I wouldn't say it's particularly complex.

On the other hand, if you need to finish in a week or less, don't have any workspace, and the task of, say, adjusting the valves makes you nervous...maybe it's best to let someone do it for you this time.

There is no "Rebuild Kits" like you can get for a Chevy; with a reground Crank and Camshafts + bearings and stuff.

The only issue I have read concerning Mercedes being differnt from other Engines is that the is a balanceing proceedrue. You would have to read the Factor Sevice Manual to get info on that. If you can reuse the Pistons and Crank Shaft as is that avoids any balancing issue.

I really would depend on the condition of your Engine.

When I was in Tradeschool what they did is if the Pistons themselves were still within specs they reused the Pistons by Boring and Sleeving the Block (this was on 180Ds). Sleeves are around $30 each while a new oversized Piston is close to $250 or more each.

The biggest stumbling block is the cost of the Parts; mainly the Pistions; if you buy European made ones. Rebuilding the Engine can easily exceed the cost of the Car when you bought it.

If there has been no Bearing Failure and the Oil/Filter Changes have been done on the Engine you might find that the Cranshaft is still within specs and can be reused as is.

The next big expense after that is if some Valves need replacing.
I have no Idea anymore what the labor cost to have even a Gasser Cylinder head overhauled. But, few people have the equipment to do that at home so that and having the Block Bored and Liners installed would be the major Labor expense.